In order for sulphur to be used as a soil additive it is essential that the sulphur be in a finely divided form and it is known to provide such prills by mixing sulphur with certain mineral clays such as bentonite.
It is well known to mix bentonite with molten sulphur and to pour the mixture into sheet form and, when it has cooled, comminute same, and separate to a predetermined particle size, but unfortunately excessive dust is produced both in the formation of the product and in the end product itself.
It is also known to produce a mixture of molten sulphur and bentonite in a pellet or prill form, and in order to prevent the undesirable premature swelling of the bentonite, to quench same in a liquid fertilizer rather than quenching the prills in water. An example of this is U.S. Pat. No. 4,133,669. Unfortunately, utilizing a liquid fertilizer coolant to form the prills results in an annealing process which is not entirely satisfactory, is difficult to control and does not give the desired compressive strength to the prill to prevent breakage during handling.